Are signals of aggressive intent less honest in urban habitats?

How anthropogenic change affects animal social behavior, including communication is an important question. Urban noise often drives shifts in acoustic properties of signals but the consequences of noise for the honesty of signals – i.e. how well they predict signaler behavior – is unclear. Here we examine whether honesty of aggressive signaling is compromised in male urban song sparrows (Melospiza melodia). Song sparrows have two honest close-range signals: the low amplitude soft songs (an acoustic signal) and wing waves (a visual signal) but whether the honesty of these signals is affected by urbanization has not been examined. If soft songs are less effective in urban noise, we predict that they should predict attacks less reliably in urban habitats compared to rural habitats. We confirmed earlier findings that urban birds were more aggressive than rural birds and found that acoustic noise was higher in urban habitats. Urban birds still sang more soft songs than rural birds. High rate...